Chapter 5 Chapter 5 Chemical Quantities and Chemical Quantities and ReactionsReactions

5.1The Mole

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Collection TermsCollection Terms

A collection term statesa specific number of items.

• 1 dozen donuts

= 12 donuts

• 1 ream of paper

= 500 sheets

• 1 case = 24 cans

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A Mole of AtomsA Mole of Atoms

A mole is a collection that contains

• the same number of particles as there are carbon atoms in 12.0 g of carbon.

• 6.02 x 1023 atoms of an element (Avogadro’s number).

1 mole element Number of Atoms

1 mole C = 6.02 x 1023 C atoms

1 mole Na = 6.02 x 1023 Na atoms

1 mole Au = 6.02 x 1023 Au atoms

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A Mole of a CompoundA Mole of a Compound

A mole • of a covalent compound has Avogadro’s number of

molecules.

1 mole CO2 = 6.02 x 1023 CO2 molecules

1 mole H2O = 6.02 x 1023 H2O molecules

• of an ionic compound contains Avogadro’s number of formula units.

1 mole NaCl = 6.02 x 1023 NaCl formula units

1 mole K2SO4 = 6.02 x 1023 K2SO4 formula units

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Samples of 1 Mole Samples of 1 Mole QuantitiesQuantities

1 mole of S atoms = 6.02 x 1023 S atoms

1 mole of H2O molecules = 6.02 x 1023 H2O molecules

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Avogadro’s NumberAvogadro’s Number

Avogadro’s number, 6.02 x 1023, can be written as an

equality and two conversion factors.

Equality:1 mole = 6.02 x 1023 particles

Conversion Factors:6.02 x 1023 particles and 1 mole

1 mole 6.02 x 1023 particles

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Using Avogadro’s Using Avogadro’s NumberNumber

Avogadro’s number is used to

o convert moles to particles

o convert particles to moles

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Converting Moles to ParticlesConverting Moles to Particles

Avogadro’s number is used to convertmoles of a substance to particles.

How many Cu atoms are in 0.50 mole of

Cu?

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Converting Particles to MolesConverting Particles to Moles

Avogadro’s number is used to convertparticles of a substance to moles.

How many moles of CO2 are in

2.50 x 1024 molecules CO2?

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ExamplesExamples

1. The number of atoms in 2.0 mole of Al atoms is

A. 2.0 Al atoms.

B. 3.0 x 1023 Al atoms.

C. 1.2 x 1024 Al atoms.

2. The number of moles of S in 1.8 x 1024

atoms of S is

A. 1.0 mole of S atoms.

B. 3.0 moles of S atoms.

C. 1.1 x 1048 moles of S atoms.10

Subscripts and MolesSubscripts and Moles

The subscripts in a formula show• the relationship of atoms in the formula.• the moles of each element in 1 mole of

compound.

GlucoseC6H12O6

In 1 molecule: 6 atoms C 12 atoms H 6 atoms O

In 1 mole: 6 moles C 12 moles H 6 moles O

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Subscripts State Atoms and Subscripts State Atoms and MolesMoles

9 moles of C 8 moles of H 4 moles of O

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Factors from SubscriptsFactors from Subscripts The subscripts are used to write conversion factors

formoles of each element in 1 mole of a compound. Foraspirin, C9H8O4, the possible conversion factors are:

9 moles C 8 moles H 4 moles O

1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4

and

1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4

9 moles C 8 moles H 4 moles O

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ExamplesExamples

A. How many moles of O are in 0.150 mole of aspirin, C9H8O4?

B. How many atoms of O are in 0.150 mole of aspirin, C9H8O4?

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Chapter 5 Chapter 5 Chemical Quantities and Chemical Quantities and ReactionsReactions

5.2Molar Mass

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Molar MassMolar Mass

The molar mass

• is the mass of 1 mole of an element or compound.

• is the atomic or molecular mass expressed in grams.

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Molar Mass from Periodic Molar Mass from Periodic TableTable

Molar mass is the atomic mass expressed in grams.

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1 mole of Ag 1 mole of C 1 mole of S = 107.9 g = 12.01 g = 32.07 g

ExamplesExamples

Give the molar mass for each (to the tenths decimal place).

A. 1 mole of Mg atoms = ________

B. 1 mole of Ag atoms = ________

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Guide to Calculation Molar Guide to Calculation Molar Mass of a CompoundMass of a Compound

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Molar Mass of a CompoundMolar Mass of a Compound

The molar mass of a compound is the sum of the molar masses of the elements in the formula.

Example: Calculate the molar mass of MgCl2.

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Element Number of Moles

Atomic Mass Total Mass

Mg

Cl

MgCl2

Molar Mass of KMolar Mass of K33POPO44

Calculate the molar mass of Na3PO4.

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Element Number of Moles

Atomic Mass Total Mass in K3PO4

Na

P

O

Na3PO4

Some 1-mole QuantitiesSome 1-mole Quantities

32.1 g 55.9 g 58.5 g 294.2 g 342.2 g

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One-Mole Quantities

ExampleExample

Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?

1) 40.1 g/mole2) 262 g/mole 3) 309 g/mole

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Molar Mass FactorsMolar Mass Factors

Molar mass conversion factors • are fractions (ratios) written from the molar mass.• relate grams and moles of an element or compound.

• for methane, CH4, used in gas stoves and gas heatersis

1 mole of CH4 = 16.0 g (molar mass equality)

Conversion factors:

16.0 g CH4 and 1 mole CH4

1 mole CH4 16.0 g CH4

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ExampleExample

Acetic acid, C2H4O2, gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.

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Calculations Using Molar Calculations Using Molar MassMass

Molar mass factors are used to convert between the grams of a substance and the number of moles.

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Grams Molar mass factor Moles

Moles to GramsMoles to Grams

Aluminum is often used to build lightweight bicycleframes. How many grams of Al are in 3.00 mole of

Al?

Molar mass equality:

Setup with molar mass as a factor:

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Learning CheckLearning Check

Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g?

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Grams, Moles, and ParticlesGrams, Moles, and Particles

A molar mass factor and Avogadro’s number convert…

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ExamplesExamples

How many H2O molecules are in 24.0 g of H2O?

1) 4.52 x 1023 H2O molecules

2) 1.44 x 1025 H2O molecules

3) 8.03 x 1023 H2O molecules

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ExamplesExamples

How many water molecules are in 3.26 g of water?How many H atoms are in 3.26 g of water?

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